California was once a part of Mexico before it became a U.S. state. Mexico gained independence from Spain in 1821 and California became a Mexican territory. However, in 1846, the U.S. declared war on Mexico and after a brief conflict, California was ceded to the U.S. as a part of the Treaty of Guadalupe Hidalgo in 1848.
Contra Costa County, located in Northern California, has a rich and diverse history that dates back thousands of years. The area was originally inhabited by various Native American tribes, such as the Miwok and Ohlone people, who thrived off the region's natural resources and lived in harmony with the land. The arrival of Spanish explorers and missionaries in the 18th century marked a significant shift in the region's history.

In 1772, the Spanish established the first European settlement in the area, known as Mission San Francisco de Asís (also called Mission Dolores), which was part of the larger Alta California mission system. The mission's purpose was to convert the indigenous people to Christianity and ensure Spanish control over the region. During this period, Spanish settlers also established ranchos, large land grants that became the foundation of the region's agricultural economy.

The 19th century brought significant changes to Contra Costa County. With the Mexican War of Independence in 1821, Spain's influence in the area waned, and Mexico gained control. During this time, Mexican rancheros maintained control over their land, but American settlers began to arrive in increasing numbers, lured by the promise of fertile land and economic opportunities.

The discovery of gold in nearby Coloma in 1848 triggered the California Gold Rush, drawing countless fortune seekers to the region. This influx of people led to the rapid growth of towns and settlements in Contra Costa County, as well as the construction of transportation infrastructure like railroads and canals. Agriculture, particularly wheat and fruit orchards, grew in prominence, and the region became known for its agricultural output.

In 1850, California officially became a state, and Contra Costa County was established as one of the original 27 counties. Over the years, the county continued to develop and urbanize, with industrialization bringing new opportunities and challenges. Today, Contra Costa County is a thriving and diverse region known for its proximity to the San Francisco Bay Area, beautiful landscapes, and vibrant communities.

This timeline provides a glimpse into the major events and milestones that have shaped the history of Contra Costa County, California.

  • 1772: Spanish explorers first arrive in the area of Contra Costa County.
  • 1821: Mexico gains independence from Spain and the land becomes part of Mexico.
  • 1849: Contra Costa County is formed as one of California's original 27 counties.
  • 1850: Martinez becomes the first county seat.
  • 1855: The county seat is moved to San Ramon.
  • 1857: The county seat is moved again, this time to Martinez permanently.
  • 1868: The Central Pacific Railroad arrives in the county, enhancing transportation and growth.
  • 1928: Construction of the San Francisco-Oakland Bay Bridge begins, connecting Contra Costa County to San Francisco.
  • 1941: The Concord Naval Weapons Station is established, playing a significant role in World War II and the Cold War.
  • 1972: BART (Bay Area Rapid Transit) extends into Contra Costa County, providing a new mode of transportation.
  • 1991: The devastating Oakland Hills Fire impacts parts of Contra Costa County.
  • 2002: Contra Costa County celebrates its 150th anniversary.